Superior the demon lord falls inlove with the Paladin whose supposed to kill her, and since I´m at it theres also Nisekoi, the two of them are from opposing yakuza families, but they are forced to be a couple.

I can't think of anything exactly as you described, but you might want to give these a look:The Demon Within - angels and demons, but a twist on which is which, not really forbidden love - in fact, the girl is supposed to choose one as a husband.Angel Sanctuary - filled with angels and demons, not sure if there is forbidden love between them, but there's some pretty wild stuff going on.Akuma na Eros - Satan and an angel are competitors for the girl. As reviewer MightyMaeve describes it, it is "simplistic and ridiculous, but a page-turner."Earthian - there is forbidden romance between angels and humans, but also between the two male main characters who are both angels.

Oh wow thanks!!! Sry if I wasn't specific.. hm but for the princess / prince thing I'm looking for something where they choose each other despite their kingdoms wishes. Not by an "alliance" . So each side completely hates each other

Princess/Prince:Bus Hashiru ~ it's a collection of stories, but the... I think last story is what you're looking for. I'm not sure if they're royalty, but the two main characters are from two opposing lands that war against each other. It's absolutely beautiful! It's colored, too.

Angel/Demon:A Fairytale for the Demon Lord ~ sort of? The leading female is angelic and has wings and there is a demon lord as the title suggests. It's a very beautiful but gory webcomic, full-colored. The plot is... Complicated.